Listronotus

Jekel, 1865

Species Guides

37

Listronotus is a of weevils in the Curculionidae containing at least 100 described . The genus includes several economically significant agricultural pests, notably the carrot weevil (L. oregonensis), (L. maculicollis), and Argentine stem weevil (L. bonariensis), as well as agents such as L. setosipennis used against weeds. Species in this genus exhibit diverse associations ranging from cultivated Apiaceae crops to pasture grasses and invasive weeds.

Listronotus lutulentus by no rights reserved, uploaded by Nick Bédard. Used under a CC0 license.Listronotus sparsus by (c) Dan MacNeal, some rights reserved (CC BY), uploaded by Dan MacNeal. Used under a CC-BY license.Listronotus squamiger by (c) Henrique Pacheco, some rights reserved (CC BY), uploaded by Henrique Pacheco. Used under a CC-BY license.

Pronunciation

How to pronounce Listronotus: /ˌlis.trəˈnoʊ.təs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Listronotus are small weevils, typically under 5 mm in length. The carrot weevil (L. oregonensis) is approximately 4 mm long, while the (L. maculicollis) reaches at most 4.5 mm. As curculionids, they possess the characteristic elongated rostrum with mouthparts at the tip. Species-level identification requires examination of specific morphological features not detailed in available sources.

Images

Habitat

vary by : L. oregonensis occurs in agricultural fields with organic and mineral-rich soils, avoiding sandy substrates; L. maculicollis inhabits golf course turfgrass and managed grasslands; L. bonariensis is found in pasturelands and cereal crops; L. setosipennis occupies areas infested with Parthenium hysterophorus. typically reside in the top layer of soil where crops have been grown.

Distribution

The has a broad distribution encompassing North America, South America, New Zealand, Australia, and parts of Africa and Asia. Specific distributions vary by : L. oregonensis occurs in the eastern United States and southeastern Canada; L. maculicollis is found in eastern North America; L. bonariensis is native to South America (Argentina, Bolivia, Brazil, Chile, Uruguay) and introduced to Australia and New Zealand; L. setosipennis has been introduced to Ethiopia and Uganda for ; L. dauci occurs in Argentina.

Seasonality

Activity patterns vary by and climate. L. maculicollis shows peak activity at temperatures between 14-17°C, with seasonal shifts in daily activity timing— in spring, early morning in summer. L. oregonensis emerge from sites when crops emerge. L. dauci begins damaging crops from September in Córdoba, Argentina, and overwinters as adults. L. setosipennis emerges from soil during rainy seasons following dry season dormancy in East Africa.

Host Associations

  • Daucus carota (carrot) - primary L. oregonensis, L. dauci, L. texanus
  • Apium graveolens (celery) - L. oregonensis
  • Petroselinum crispum (parsley) - L. oregonensis, L. latiusculus
  • Poa annua (annual bluegrass) - primary L. maculicollis
  • Lolium perenne (perennial ryegrass) - L. bonariensis
  • Parthenium hysterophorus - L. setosipennis; used for
  • Various Poaceae (grasses) - L. bonariensis

Life Cycle

Complete with four life stages. L. dauci completes development in 39-44 days at 24°C: hatch in 10-12 days, larval development spans 10-16 days, and lasts 5-9 days. L. oregonensis larvae pass through four instars while tunneling through plant crowns toward roots. L. bonariensis exhibits major fluctuations in stage densities across seasons. occurs as in soil for multiple .

Behavior

L. oregonensis are capable of but primarily walk when dispersing, even for to new fields. They show strong negative response to sandy soils, moving away rapidly. L. maculicollis activity is driven more by temperature than light cycles, with at 14-17°C. L. setosipennis demonstrates seasonal from soil following dry periods. selection involves female assessment of plant suitability for oviposition.

Ecological Role

Herbivores with variable impacts: some function as significant agricultural pests causing crop losses and plant mortality through larval tunneling, while others serve as agents against weeds. L. bonariensis is a major pasture pest in New Zealand. L. setosipennis contributes to suppression of Parthenium hysterophorus in East Africa. Ground beetles (Carabidae) and (Mymaridae) act as natural enemies of some species.

Human Relevance

Multiple are economically important pests. L. oregonensis is described as the most damaging insect pest to carrot growers in Ontario. L. maculicollis is the single most destructive insect pest of golf course turfgrass in eastern North America. L. bonariensis causes significant losses in pasture and cereal production. Management relies heavily on foliar , crop , and emerging methods including . L. setosipennis has been deliberately introduced for of Parthenium weed in Ethiopia and Uganda.

Similar Taxa

  • HyperodesL. maculicollis was formerly classified as Hyperodes sp. near anthracina-anthracinus; historical taxonomic confusion
  • Other CurculionidaeSmall size and plant-associated habits require careful morphological examination for -level identification

More Details

Biological Control Potential

show promise for management of L. oregonensis, with Steinernema carpocapsae achieving 88% mortality in sandy soil and Heterorhabditis bacteriophora 81% in muck soil under laboratory conditions. However, field application remains limited by cost and constraints.

Research Gaps

Behavioral of Listronotus remains poorly understood, including mate-finding mechanisms, preferences among cultivars versus wild plants, and patterns between sites and new fields. No attractants, repellents, or have been identified for management use.

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Sources and further reading